System and Method for Transferring Non-Compliant Packetized and Streaming Data Into and From a Multimedia Device Coupled to a Network Across Which Compliant Data is Sent

ABSTRACT

A communication system, network, interface, and port architecture are provided for transporting different types of data across a network. The network can be arranged by connecting the ports in a daisy chain fashion to achieve a ring architecture or topology. The network forwards data according to a specific network protocol, and any incoming data that follows that protocol will be sent onto the network. If the incoming data protocol does not match the network protocol, then the incoming data is not sent immediately to the network, but instead is sent to an input pin of a device upon the network specifically designed to receive that incoming data. The network, therefore, has ports that support both compliant and non-compliant incoming data, and the devices that produce such data. Examples of non-compliant data include any data which does not time-division multiplex different asynchronous, isochronous, and synchronous data in dedicated channels within each frame, and which have a preamble, coding, frequency, or overall protocol different from that which is established for network transfer.

CONTINUING DATA

The present application is a divisional from prior U.S. patentapplication Ser. No. 10/859,470 filed Jun. 2, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a communication system and, more particularly,to a synchronous communication system formed as a ring network of two ormore ports coupled in daisy chain fashion to one another to allowcommunication to and from a external multimedia device coupled to atleast one port of the network to complete the ring. The ports arepreferably associated with a single multimedia device, and the networkis formed between ports of the device to which the external multimediadevice is coupled so that the port can accommodate data that conforms toa particular protocol used by the network (i.e., complaint data), or theport can accommodate non-compliant data as asynchronous Ethernet-basedpackets of data, synchronous or isochronous data, analog data, and/orSony/Philips Digital Interface Format (“SPDIF”) data.

2. Description of the Related Art

A communication system is generally known as a system that permitscommunication between nodes interconnected by a transmission line. Eachnode can transmit information, or can transmit and receive information,across the transmission line. The communication system of interconnectednodes can be organized in various topologies, such as bus, ring, star,or tree topology.

A bus topology network is generally regarded as linear, wheretransmissions from one node propagate the length of the transmissionline and are received by all other nodes connected to that bus. A ringtopology network, however, generally consists of a series of nodesconnected to one another by unidirectional transmission links to form asingle, closed loop. Examples of a ring network are described in IEEE802.5 and Fiber Distributed Data Interface (FDDI).

The transmission line between nodes can be either wired or wireless. Itis preferred that the transmission line accommodate different types ofdata. Unfortunately, certain portions of a network may be tailored tosending bursts of data, such as TCP/IP across Ethernet, while otherportions may be called upon to send streaming data, such as audio andvideo data. It would be desirable to introduce a network that cantransfer both types of information, in whatever form, upon the network.Moreover, it would be desirable to use, for example, copper wire, fiberoptic, or wireless transmission medium for the chosen transmission line.

Ethernet and IEEE 802.03 specify a particular protocol in which packetsof data can be sent between computing systems. Ethernet can sensemultiple access collisions and can arbitrate which source device willgain mastership over the transmission line. Ethernet operates at thelowest levels of the OSI reference model, normally reserved for the datalink and physical link layers. The Ethernet protocol specifies aparticular frame format of a preamble, followed by a destination addressand a source address, and then the data payload. The data is generallyencoded in a 4B/5B or 8B/10B encoding structure prior to the data beingsent across the coax or twisted pair transmission line.

The encoded packets of data sent within an Ethernet frame generally haveno time relationship relative to each other. For example, a computer cansend a burst of data in several successive frames, and then aconsiderable amount of time might pass before the next burst of data issent. Bursty or packetized data need not be sent as real-time,time-related data since the packets are typically stored and used laterby the destination device.

Conversely, streaming data has a temporal relationship between samplesproduced from a source port onto the network. That relationship betweenthose samples must be maintained across the transmission line to preventperceptible errors, such as gaps or altered frequencies. A loss in thetemporal relationship can cause a receiver at a destination toexperience jitter, echo, or in the worst instance, periodic blanks inthe audio and video stream.

Packetized TCP/IP data, for example, placed in an Ethernet frame neednot maintain the sample rate or temporal relationship of that data andnetworks that send packetized data typically send that data at whateverrate the source device operates. Thus, a network that forwardspacketized data is generally considered as an asynchronous network.Conversely, a network that forwards streaming data is generallysynchronous, with each source and destination node sample at a ratesynchronous to the network.

While streaming data is typically sent synchronously across a network,there may be instances in which the sample rate (fs) local to a node isnot at the same frequency as the frame synchronization rate (FSR or FSY)of the transmission line. If this is the case, then the data streamingfrom a source device can be sample rate converted, and then sentsynchronously across the network. Alternatively, the data can be sentisochronously across the network.

There are various types of sample rate converters available on themarket. For example, Analog Devices Corp. offers part no. AD1896 toconvert the sample rate offered by the local clock to another samplerate synchronous to, for example, another clock associated with thenetwork, for example. Either increasing or decreasing the sample ratewould be beneficial if a system can be employed that can match fs toFSY. Sample rate conversion, however, oftentimes involves fairly complexalgorithms for comparing fs to FSY, and generally a digital signalprocessor (DSP) is used at the source node. If, for example, the sourcenode contains compressed data, such as AC3 data streaming from a DVD,the compressed data must be decompressed before the data is sample rateconverted. Unfortunately, sending decompressed data consumes morenetwork bandwidth than sending compressed data.

It would be desirable to implement an improved communication system ornetwork. The improved network should be one that can accommodatestreaming data in either synchronous or isochronous form. The datastreaming from a source node should be sent isochronously rather thansample rate converted. Moreover, the improved network should alsoaccommodate packetized data in order to interface computing systems,such as computers and interactive televisions, to streaming audio andvideo data accessible by such systems.

FIG. 1 illustrates a system made up of nodes that send and receivepacketized and streaming data yet, however, communication between suchnodes is limited due to the constraints of the different protocols bywhich data is transferred. As shown, a communication system 10 mighthave an audio/video receiver 12. Receiver 12 operates essentially as adual-purpose switch or “hub” for streaming data sent between, forexample, an MP3 player 14, an audio tuner 16, a DVD player (or DVR) 18,and CD player 20. Receiver 12 can receive the streaming data from thevarious players or inputs and forward the serial bitstream afterprocessing to, for example, an amplifier, speakers 22, and/or digitaltelevision 24.

The information sent from the various devices 14-20 can be sent toreceiver 12 as analog data or digital data. A popular format for digitaldata is the Sony/Phillips Digital Interface Format (SPDIF). SPDIF wasestablished by the Audio Engineering Society (AES) in conjunction withthe European Broadcasting Union (EBU) to create a standard interfaceknown as the AES/EBU interface. The interface constitutes a serialtransmission format for linearly-represented, digital audio data. Theformat is generally independent of sampling frequency, but threesampling frequencies are nonetheless recommended by AES for pulse codemodulated (PCM) application: 32 kHz, 44.1 kHz, and 48 kHz. The SPDIFprotocol and frame structure is well documented as a series of 16-bitbytes, beginning with control and category codes, as well as the sourcenumber and channel number by which data is transferred from a digitalsource, such as a CD, DVD, or MP3 player.

The SPDIF protocol can, for example, be used by a digital television(DTV) 24, and a packet hub 26 can be used to combine packetized datafrom, for example, a digital video broadcast (DVB) receiver sometimesknown as a set top box 28. Certain commands broadcast from the set topbox 28 can be forwarded to hub 26, while streaming data is forwarded tothe audio video receiver 12. The command signals that emanate from settop box 28 can be sent as, for example, TCP/IP data within the networklayer of the OSI model, which is then wrapped with the Ethernetprotocol, recognizable to hub 26. Along with the Ethernet packets fromthe set top box 28 and digital television 24, hub 26 can also receiveEthernet packets from a personal computer (PC) 30. The packets ofinformation processed by hub 26, therefore, can constitute controlinformation.

It may be desirable to implement interactive television processing inmultiple rooms throughout a user's home, or in different homes orlocations. For example, another DTV 32 can be situated in a second room,separate and apart from DTV 24 placed in a first room. Alternatively,DTV 32 can be a computer laptop carried outside the home in which DTV 24resides. Similar to DTV 24, an audio amplifier 34 might form a part ofDTV 32 or be built outside DTV 32 and, as shown, receives either digitalor analog information. If in digital form, the information can be sentpossibly in SPDIF format to amplifier 34, which then processes thedigital information and outputs the information to the appropriate leftand right speakers, or multiple surround speakers 36.

A prevalent problem with home or consumer audio/video electronics is therapid advances in digital interaction to those electronics via, forexample, PCs. Interacting home electronics with PCs is difficult at bestsimply due to the differences between asynchronous networks andsynchronous networks. Network 10 of FIG. 1 attempts to combineasynchronous, packet-processing nodes or devices with synchronous,streaming nodes or devices. However, the streaming information cannot bereliably sent to DTV 32 if DTV 32 cannot gain mastership of theasynchronous bus 38. This will entail possible loss of streaming dataupon DTV 32.

There have been attempts to overcome the problem of interfacingasynchronous transmission lines to synchronous transmission lines inorder to network audio and video data. For example, a product known asCobraNet attempts to eliminate the dropouts and discontinuities ofstreaming data sent across an asynchronous network. CobraNet providersrecommend using dedicated Ethernet network for audio, and anotherdedicated Ethernet network for the packetized data. See, Harshbarger andGloss, “Networking for Audio, Part 3,” 2004, herein incorporated byreference. Requiring two separate Ethernet networks and maintaining theasynchronous protocol between nodes substantially increases the overheadof the network, and the complexity of software and hardware drivers usedby that network.

It would be desirable to introduce a network that can transfer streamingdata (both isochronous and synchronous streaming data), as well aspacketized TCP/IP data and control data simultaneously across a network.It would also be desirable to send the various types of data across anetwork that is clocked at the same rate for all such types of data.Thus, the desired network is a synchronous network where sampled,streaming data is cognizant of the network transfer rate, and packetizeddata is placed onto the network at the network transfer rate. Moreover,the improved network avoids utilizing two transmission paths for audioinformation and packetized data. Any multimedia device which streamsdata or sends bursts (packets) of data can be formatted and time-slottedonto the desired communication system and network.

SUMMARY OF THE INVENTION

The problems outlined above are in large part solved by a communicationsystem and network made up of a multimedia device having ports coupledtogether to complete a network to which a second multimedia device canbe coupled. Each port is used to determine whether an incoming bitstreamfrom the second device is in compliance with the network protocol ornot. If so, then the compliant data is forwarded into the appropriatetime slot of the network packet. If not, then the non-compliant data isnot directly placed onto the network but instead is recognized by aninput of the first device specifically designed to accept thenon-compliant data. An interface within the port can be used toreformat, if needed, the non-compliant data and to output it from thefirst port and into a bypass input of a second port via the ringnetwork. The output from the first port is coupled onto the network paththrough a bypass output pin of the first port.

As used herein, a multimedia device is any device that sends or receivesdata in whatever form. Examples of multimedia devices include multimediahubs, switches and audio processors (i.e., audio and/or videoreceivers), computers, amplifiers, speakers, multimedia players (i.e.,CD players, DVD players, MP3 players etc.), multimedia recorders (i.e.,VCRs, DVRs, etc.), and GPS systems. The term multimedia device ishenceforth referred to simply as a device.

The network protocol used by the present system involves a preamble thatestablishes a channel between a source device and a destination device,where the destination device can be any device connected to the networkof interconnected devices that is configured in a ring topography. Eachframe following the preamble consists of a time-division multiplexed setof fields reserved for respective channels of communication. Forexample, the first field might be reserved for synchronous streamingdata, the second for streaming isochronous data, the third forpacketized data, and the fourth for control data. Thus, multimediadevices coupled to the ring can send in each frame at least one type ofdata. The frame transfer rate (FSY) is synchronized to the sample rateor, alternatively, if the sample rate is higher or lower than FSY, thenstreaming data can be sent isochronously within a particular time slotor channel, established about the ring network. Therefore, each framesends contiguous channels of streaming data from a source device to adestination device, without time-interruption between frames. As thestreaming data is sampled on the source device, it is sent in real-timeacross the network within one of possibly N number of channels or fieldswithin a frame, sent at the same rate or possibly integer multiples offs.

The protocol used by the synchronous network hereof involves specifictime-division, multiplexed channels reserved in each and every frame.Each channel is designated for a particular type of data transfer,whether the data type is synchronous, isochronous, packet, or controldata. In order to interface with that network protocol, it is imperativeto recognize incoming data from a multimedia device as either data thatfalls within that protocol or outside of that protocol. Data which istimed relative to a frame sync pulse, or FSY, as a particular type ofdata offset in time from the FSY pulse for a designated time slot (i.e.,time-division, multiplexed channel) will be compliant with the networkprotocol. Otherwise, the incoming data will not be recognized as beingwithin one of the time-division, multiplexed channels reserved for aparticular type of data within that channel, and thus is non-compliant.There are multimedia devices that can send non-compliant and/orcompliant data and are referred to as non-compliant device or compliantdevices, respectively.

A digital-to-analog converter (DAC) typically sends analog signalsmodulated possibly according to frequency that is dissimilar to thefrequency used by the synchronous network. Typically, analog signalsrange somewhere near 20 Hz-20 kHz, or possibly wider, but certainly muchless than the transfer rate of the network which can be much higher than30 kHz and, more preferably, 44.1 kHz or 48 kHz. Although SPDIF data canbe sent at 44.1 kHz or 48 kHz, SPDIF data uses a preamble that isdissimilar from the preamble of data sent across the network. Also,SPDIF data is not time-slot allocated in accordance with the networkprotocol that accommodates multiple types of streaming and packetizeddata. Still further, packets of data sent according to the Ethernetprotocol use a protocol different from that used by the network sinceTCP/IP data within the Ethernet packet is not targeted for a specifictime slot of a frame that is regularly sent at an FSY rate, nor is thepreamble for packetized data sent as broadcast channels synchronouslyacross the network.

Analog signals, Ethernet packets, and SPDIF data are transferred at avariable frequency different from the network, transferred at afrequency asynchronous to the network, and/or transferred using apreamble or coding algorithm altogether different from the compliantpackets sent across the network. Thus, analog, packetized, and SPDIFdata, and possibly other types of data, not consistent with thefrequency, amplitude, preamble and coding of the network packets/frames(i.e., the network protocol) are herein referred to as non-conformal ornon-compliant data. Multimedia devices that send non-compliant data are,therefore, referred to as non-compliant devices or simply “legacy”devices.

Until the legacy devices can transfer data in the appropriate time slotand at the network transfer rate, the present network implements a portthat will accommodate the legacy devices and their associated databitstreams. However, some devices may comply with the network and,therefore, the port can also recognize complaint devices and theirassociated data bitstreams. The present network and communication systemcan connect multimedia devices with one another to form a ring, witheach device connected to a port that can recognize and appropriatelydirect either compliant or non-compliant data sent from each device. Theport can receive incoming data from a compliant device onto the network,or can receive incoming data from a non-compliant device into a pindesignated to receive the non-compliant data.

According to one embodiment, a pair of communication ports is provided.Both ports can be associated with a first multimedia device. The firstport has a first port receive input, a first port bypass input, and afirst port output. The second port has a second port receive input, asecond port bypass input, and a second port output. The first portoutput is coupled to the second port bypass input to form a networkamong the pair of ports (first and second ports). The network allows asecond multimedia device to couple incoming data onto the network pathand/or communicate with the first multimedia device associated with thefirst and second ports. If the incoming data from the second multimediadevice is conforming to (i.e., is complaint data), then the incomingdata can be placed into an appropriate timeslot of the network frame,and the data continues through the first port from the first port bypassinput to the first port output, and then into the second port bypassinput to the second port output, and back around to the first portbypass input—if only two ports are provided. If the incoming data is notcomplaint, then the incoming data is placed into an input of the firstmultimedia device specifically designated to receive this data, andmeanwhile the network continues from the first port bypass input to thefirst port output, which includes the first port bypass output. The pinis one that preferably receives serial data and, once the non-compliantserial data is processed, it can be reformatted by an interface circuitor system within the first port, if desired, to a format that iscompatible with the network protocol. Thus, the reformatted,non-complaint data can be made complaint after it is processed by aninterface circuit associated with the first port. Other ports of thenetwork have a similar interface circuit, which preferably comprises adigital signal processor (DSP) that processes the incoming data and aphysical layer transceiver device, or controller, that reformats theincoming data to make it complaint to a particular time slot reservedfor that type of data.

According to one embodiment, the first port associated with the firstdevice can compare the protocol and a time-division structure of eachframe of data transferred across a ring network through the first port,second port, and so forth associated with the first device with theprotocol of the incoming data from the second device to determine if theincoming data is compliant with the network protocol. If it is, then theincoming data is said to be sent from a compliant device. If it is notcompliant, then the incoming data is sent from a non-compliant, legacymultimedia device. SPDIF, analog signals, and packetized (i.e.,Ethernet) data is typically regarded as non-compliant data fromnon-compliant devices.

A port of the first device can accommodate incoming data from either acompliant or non-compliant device. If it is desirous to connect bothcompliant and non-compliant devices to the first device, then preferablythe first device includes two ports: one port for each connection. Thetwo ports are connected through bypass input/outputs so that each portincludes two inputs (a receive input for receiving incoming data and abypass input) and two outputs (a transmit output for sending outgoingdata and a bypass output). The bypass output is coupled to a bypassinput of the next port within the series of ports. The bypass outputfrom the last port in the series is coupled to a bypass input of thefirst port in the series to complete the ring network.

Each port includes an auto detect detector/comparator and multiplexercircuit operably coupled to compare the data sent across the network toincoming data, and forward the incoming data onto the network via abypass output if the incoming data is in a format similar to the networkprotocol. The port might include a phase-locked loop having a frequencymultiplier and divider for slaving a sampling rate of incoming data to atransfer rate of the data sent across the network. Alternatively, atleast one bit can be sent with the incoming data representative of aphase difference between the phase of the incoming data and the phase ofdata sent across the network. The phase difference information containedin the bit value can then be used, along with the data transfer rate ofthe network, to recompile a sampling rate at the destination node, ordevice. In instances in which a phase-locked loop exists at the sourceand destination, slaved from the network transfer rate, representsoperation in a locked isochronous mode of transfer. Instances in whichat least one bit is sent along with the data across the networkrepresenting phase differences is referred to as an unlocked isochronousmode of transfer. Regardless of which mode of operation is chosen, datacan be sent isochronously across the network if the sample rate on thesource or destination device is different from FSY of the network.

According to yet another embodiment, a communication system is providedthat includes a first device having a first port that includes a firstport receive input and a first port transmit output. A second multimediadevice has a second port that includes a second port receive input and asecond port transmit output. The first port receive input and secondport transmit output are coupled together to transfer digital data andright analog audio data. The second port receive input and first porttransmit output are coupled together to transfer digital data and leftanalog audio data. The first device can include an analog-to-digitalconverter (ADC), whereas the second device can include adigital-to-analog converter (DAC), or vice versa. The first device canalso include a third port. The first port can include a first portbypass input and a first port bypass output, and wherein the third portcan include a third port bypass input and third port bypass output. Thefirst port bypass output is preferably coupled to the third port bypassinput. The first port can further include a serial input pin and amultiplexer. The serial input can be a pin on an interface circuit thatincludes a processor, into which all incoming data is sent. The serialinput receives all incoming data, including non-compliant data. Theright analog audio data and/or the digital data placed into the firstport receive input can be directed to either the serial input pin, ifcompliant data, or onto the first port bypass output via placement intoa receive input on the interface circuit, if non-compliant data.

BRIEF DESCRIPTION OF THE DRAWING

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to theaccompanying drawings in which:

FIG. 1 is a block diagram of various devices coupled together in anunsuccessful attempt to send streaming and packetized data therebetween;

FIG. 2 is a plan diagram of a protocol used to send multiple frames ofcomplaint data across a network based on time slots reserved for eachtype of data;

FIG. 3 is a block diagram of complaint and non-compliant devices coupledto ports of a device (such as an audio video receiver) to form a ringnetwork, with a port shown in detail for transferring compliant dataonto and from the network;

FIG. 4 is a block diagram of a non-complaint SPDIF or packet (drivenover Ethernet) device coupled to a port shown in detail for transferringnon-compliant SPDIF data into and from a device associated with the portand, if needed, for reformatting the non-compliant data and placing itonto the network;

FIG. 5 is block diagram of a comparator used to compare the protocol(preamble or coding) of digital signals from a device coupled to theport to determine whether to forward the digital signals onto thenetwork, or initially into a device associated with the port and thenonto the network;

FIG. 6 is a block diagram of a non-compliant DAC device having a leftchannel output coupled to a transmit pin of a first port and a rightchannel output coupled to a receive pin of the first port, and then froma second port receive pin coupled to a left channel input and a transmitpin coupled to a right channel input of a non-compliant ADC device,wherein both first and second ports are shown in detail for couplingnon-compliant DAC data into a device associated with the port and, ifneeded, for reformatting the non-compliant data and placing it onto thenetwork and back out to the DAC device;

FIG. 7 is a block diagram of a comparator used to compare amplitude orfrequency of an analog signal from a device coupled to the port todetermine whether to forward the analog signals onto the network, orinitially into a device associated with the first port and then onto thenetwork;

FIG. 8 is a block diagram of a DVD device having a pair of ports throughwhich compliant and non-compliant data can be sent from an AV receiverdevice, according to one exemplary configuration;

FIG. 9 is a block diagram of a source device driving sampled data into asource port having a phase and/or frequency comparator and forwardingunlocked isochronous data along with phase and/or frequency differencesbetween the source sample rate and the network frame rate across thenetwork where a destination port implements a digital PLL to lock adestination sample rate from the phase and/or frequency difference;

FIG. 10 is a block diagram of an AV receiver device with a pair of portsthrough which complaint and non-compliant data can be sent from acompliant DVD device and a non-compliant CD device, according to oneexemplary configuration; and

FIG. 11 is a block diagram of a source device driving sampled data intoa source port and a destination device that receives the sampled data aslocked isochronous data, wherein both the source port and destinationport include a PLL that samples at a frequency locked to andproportional to a frame sync frequency of the network.

While the invention is susceptible to various modifications andalternative forms, specific embodiments hereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and detaileddescription thereto are not intended to limit the invention to theparticular form disclosed, but on the contrary, are intended to coverall modifications, equivalents, and alternatives falling within thespirit and scope of the present invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

It is recognized that one or more multimedia devices can sample data ata higher sampling rate (fs) than the frame sync rate (FSY) of atransmission line. For example, a multimedia device can be a CD playerthat samples at approximately 44.1 kHz. The CD player can stream dataat, for example, 16 bits per sample audio channel (32 bits/stereochannel), therefore, resulting in a bps Baud rate across thetransmission line of 32 bits/stereo sample×44.1 K samples/second=1.4112Mbps. The non-return to zero (“NRZ”) data from the device can be encodedin several ways. Data can also be encoded using, for example, the wellknown Miller encoding technique.

Alternative encoding includes bi-phase encoding, or encoding so that theencoded bit stream does not incur an accumulated DC value. The latterencoding mechanism is oftentimes referred to as DC-adaptive or DC-freeencoding, and is described in U.S. Pat. No. 6,437,710 hereinincorporated by reference. If FSY across the transmission line isdifferent than the sample rate fs, then the streaming data from themultimedia device cannot be placed synchronously through thetransmission line to another device (i.e., from a DVD player to aspeaker). Instead, the streaming data must be placed as isochronousstreaming data as opposed to synchronous streaming data. Other types ofdata as described above can also be placed across the network.

Asynchronous data or packetized data can be arranged as datagrams, usingthe Transmission Control protocol (TCP) and the Internet protocol (IP).TCP/IP are the fragmented datagrams placed in an IP packet format.However, when the TCP/IP packet is forwarded across a network, thetransport and networking layer of the OSI reference model can be sentaccording to a data layer or physical layer of the OSI reference modelaccording to, for example, the Ethernet protocol. The datagrams alonecan be removed from the Ethernet protocol and sent using a differentprotocol if desired. FIG. 2 illustrates TCP/IP datagrams along withother types of data sent using a network transmission protocolindigenous to the present network.

Turning now to the drawings, FIG. 2 illustrates a format by whichdifferent types of data are sent across a network within each and everyframe being transferred. Following a preamble synchronized to abyte-wide FSY, a protocol can be established within the preambledesignating certain channels formed between a master and slave unitconnected to the network. Thereafter, each frame begins with an FSY bytevalue that is uniquely discernable, such as a coding violation, followedby a first time slot dedicated to receiving synchronized data, andsecond time slot dedicated to receiving packetized data, a third timeslot dedicated to receiving isochronous data, and a fourth time slotdedicated to receiving control data.

Each time slot represents a channel. For example, there may be fourchannels within a frame structure of 64 bytes, and each channel can havea minimum of 2 bytes. If each channel has the same number of bytes, thenthe 64 bytes can be broken into 16 bytes each that repeats at an audiosample rate of a device connected to the network via a node. Forinstance, if the audio sample rate is 48 kHz, the total bit rate of thenetwork between any two nodes is 48 K/frames sec.×64 bytes/frame×8bits/byte=24.576 Mbits/sec.

When a device is activated or “powered up,” routing tables are broadcastacross the control channel to each of the other devices upon thenetwork. The control channel contains configuration (or reconfiguration)routing tables needed to accommodate data transfer between the newlyactivated device(s). The routing table is, therefore, created toaccommodate all of the various channels or frame portions established toreceive the various types of data, thereafter synchronously sent acrossthe network between activated devices. The routing table within a memorymedium of, for example, a DSP will then identify which bytes within aframe is associated with a particular channel when subsequentcommunication is desired.

Thus, for example, if a DVD is on one channel and a CD on anotherchannel, the routing table will actually assign time slots to thosechannels. In this fashion, the DVD player will send audio and videoinformation within a first channel, yet the CD player will send audioinformation within a second channel allocated according to time slots.If the network transfer rate is 48 kHz, then a DVD player that samplesat 48 kHz and a CD player that samples at 44.1 kHz will allocate thesynchronous data channel to the DVD player, and the isochronous datachannel to the CD player.

Isochronous data can have, for example, a variable channel length alsoestablished within the routing tables when, for example, a computerconnected to the network comes on-line. For example, if an isochronoustransfer requires an additional byte within successive frames (shown inFIG. 2 as N+1 bytes), then the routing table will assign that byte when,for example, a high frequency sampled DVD player comes on-line and isactivated to a network previously locked to a lower transfer frequency.A decoder will recognize and decode the synchronization byte (FSY) andforward the control byte to the processor, which then updates therouting table within the corresponding node. The synchronization byte isforwarded to a timer within the interface controller, for example. Thetimer will ensure that the bytes sent across the network aresynchronized with the switch in order to appropriately route data to thedestination or target at appropriately timed byte boundaries.

The four time slots shown in FIG. 2 are applicable to a single frame. Itis understood, however, that multiple frames are sent in sequence. Eachframe maintains transmission of time slots and channels according to therouting tables. As devices are brought on-line, the routing tables areupdated and time slots are allocated. If, for example, a single pair ofdevices are on-line, then possibly the entire frame can be allocated toa single frame segment to accommodate data transfers between thosedevices. If the data is streaming, the routing tables are defined toallocate at least one frame segment across all frames sent within thenetwork during times when the streaming source is active. Thus, a framecan be repeated and is sent in sequence to a decoder from, for example,a source device within a node on the network.

There may be instances in which, for example, both a telephone and a CDmay be sampling data at the same rate in which the network data is beingclocked. In this case, two frame segments or time slots are reservedwithin each frame for carrying synchronous data. In this example, therecertainly can be more than four time slots, with two or more time slotsdedicated to receiving synchronous data and, possibly, another two ormore dedicated to receiving isochronous data if, for example, a pair ofhigher or lower sampling rate players can be activated on the network.

Time slots TS0-TS3 are shown merely as an example and are available ascorresponding segments within each frame, beginning with frame 1 andending with frame N. If the network is operating at a lower FSY than asample rate (fs) of a particular device, then possibly another byte willbe needed for the segment carrying isochronous data. A typical examplemight be a network locked to a CD output sampled at 44.1 kHz attemptingto place a DVD player information sampled at 48 kHz. In order toaccommodate the higher sampling rate of the DVD drive, an additionalbyte is placed within the isochronous segment of, for example, time slotTS2.

Regardless of the data type being sent, each channel of data sent acrossthe network is transferred at the same rate. This allows the network tooperate synchronously while accommodating what is normally data that issent asynchronously, or data that is sampled at a higher or lower ratethan the network transfer rate (i.e., isochronous data). Each time slotor channel is thereby synchronous with one another. Transferring thechannels synchronously is implemented by allocating an additional byteto the synchronous transfer of isochronous data.

While the isochronous data is sent at the same transfer rate as theother channels, a signaling byte is used to identify which of the Nbytes (if the sample rate is less than the frame sync rate) or N+1 bytes(if the sample rate is greater than the frame sync rate) in each frameare valid. For example, if the network is operating at 48 kHz and it isdesired that a device sample onto the network at 44.1 kHz, then aminimum of 8×44.1/48 bytes/frame or 7.35 bytes/per frame are needed toaccommodate an 8 byte per frame isochronous channel. In this examplewhere N=8, a minimum of 8 bytes per frame are needed to accommodate thisisochronous data, yet only a portion of the 8 bytes in each frame areactually valid.

The signaling byte will keep track of which of these frames are validand which are not. Thus, the isochronous data is synchronized off of thesignaling byte. For reasons described later, a tag byte can be used tosynchronize packetized data, and to indicate where within each frame thepacketized data exists and is valid. The signaling byte can be embeddedwithin the data itself and can represent a coding violation, forexample. A coding violation dissimilar from, for example, the DCA orDC-free coding of U.S. Pat. No. 6,437,710 will indicate whereisochronous, asynchronous, and/or synchronous data are to be placedwithin each frame by signaling the beginning of a series of bytes whichoccupy that frame segment, as well as one or more successive framesegments until the end of that message has arrived. The time betweenwhen a data code violation occurs will then symbolize a channel, wherethat channel can encompass different data types.

FIG. 3 illustrates a synchronous network 40 of interconnected ports 42,44, and 46 that form inputs/outputs of a device, such as an AV receiver,or multimedia data hub 41. Ports 42, 44, and 46 are coupled togetherthrough bypass out (BO) to bypass in (BI), where the last port 46 of thechained series of ports has a BO coupled to BI of the first port 42 ofthe series to form a loop, or ring network 43. The loop can be completedwhen coupling the transmit of port 42 to the receive of device 50 a, andthen the transmit of device 50 a back onto the receive of port 42 viadetector and multiplexer circuits. A loop can also be formed throughdevices 50 b, 50 c or 50 d. As shown, BO of port 42 is connected to BIof port 44, and BO from port 44 is connected to BI of port 46, and BO ofport 46 is connected to BI of port 42. For sake of brevity of thedrawing, only three ports are shown. However, it is understood that aminimum of two ports is generally desired, but that more than threeports can be used, if needed.

Within each port is a detector (or comparator) 45 b and a pair ofmultiplexers 48 a and 48 b, as indicated by the detailed, blow upillustration of port 42. Multiplexer 48 a receives BI from the networkand serial output, TX, from the AV receiver device. Depending on whetherthe external device 50 a is compliant or non-compliant, then multiplexer48 a will select compliant data within BI for input into the RX pin ofdevice 50 a, or multiplexer 48 a will select non-compliant data from thetransmit pin, TX, of device 41 for input into the RX pin of device 50 a.Auto detect of the incoming data is not needed, knowing data output onthe TX pin of device 41 is non-compliant. Detector 45 b and multiplexer48 b are attributed to the BO and RX of the audio-video (AV) receiverdevice 50 a. Transmit output of device 50 a is coupled to receive inputof port 42. An auto detect is performed by detector 45 b, andmultiplexer 48 b will either send the signal upon the receive input toBO of port 42 or the BI will be sent, depending on whether the incomingdata is compliant or not. The incoming RX data is placed on one of theinput pins of the detector 45 b and multiplexer 48 b, with BI placed onthe other input pin. The auto detect function is performed withindetector 45 b to compare the incoming data protocol to the networkprotocol to determine if the incoming data is from a compliant ornon-compliant device.

The incoming data on the RX pin of port 42 is placed into both detector45 b and a receive pin of an interface, which will eventually lead thedevice 41. The data on BI can be routed to 41, if needed, through a portconnecting a controller that receives BI placed on BO. As shown in FIG.3, the incoming data on ports 42 and 46 are from a compliant device,whereas the incoming data on port 44 is from a non-compliant device.Multiplexer 48 a perform similar functions as multiplexer 48 b, exceptthat data from the device 41 and BI are selected by multiplexer 48 aand, depending on whether the targeted device 50 a is compliant or not,either the data from device 41 (via TX of an interface associated withdevice 41) or BI is placed onto the outgoing data TX of port 42.

Device 50 a is a compliant device that sends/receives data according tothe network protocol described above, with channel information ofchannel A placed in the appropriate time slot and, thus, detector 45 band multiplexer 48 b will compare and route the appropriate data to thereceive pin, RX, associated with an interface of device 41. Thus, theincoming data on the RX pin of device 41 can be processed and coupledinternally through an interface circuit and associated transceivercontroller via, for example, an I²C or I²S port to the BO of port 42 toprocess the incoming data by device 41, but also to send the incomingdata on RX pin or the incoming data BI of the network data to otherdevices 50 b, 50 c and/or 50 d, if needed. Details of the interfacecircuit used to couple BO through a controller to the input of device 41is described below in reference to FIG. 8.

If a device is non-compliant, such as device 50 b, then it is uncertainwhere the data of a particular channel (i.e., channel C) is to be placedsince the protocol is unrecognizable to the network protocol, asdetected by the auto detect circuitry within device 44. Thus, port 44receives the incoming signal on the serial input pin as well as themultiplexer. The multiplexer within port 44 will select the BI forcoupling onto BO to continue the network, but will allow device 41 toreceive the non-compliant data via the serial input pin, SR. Decision onwhether the incoming data placed on the RX input is compliant or not ismade within, for example, a DSP. Similar to device 50 a, devices 50 cand 50 d are compliant devices that send channel of information within aparticular dedicated slot, such as channel E as shown. Devices 50 c and50 d can be coupled within the ring to expand the ring network toinclude more than two devices.

FIG. 3 illustrates in all instances the transfer of compliant dataaround a network from the TX pin of a second device 50 a (or any otherexternal device) into the RX pin of a first device 41, and consequentlyto another external device 50 c of a next, successive device to form thering. If non-compliant incoming data is received, then the incoming datawill not be placed immediately onto the network, but can be placed onthe serial input pin of the device and processed according to whateverprotocol the incoming data provides and, therefore, is acceptable to theserial input pin designed to handle that non-compliant data.

FIG. 4 illustrates a certain type of non-compliant data, such as SPDIFstreaming data or Ethernet packetized data. If the incoming data fromthe TX pin of a non-compliant device 50 b arrives across a transmissionchannel 52, then the non-compliant (SPDIF or Ethernet) data is comparedby detector/comparator 54 b with the data sent across the networktransmission path. If the protocol is different, then a comparatorsignal (C) is sent from comparator 54 b to select network data from BIto be sent to BO via multiplexer 58 b. The incoming RX data is forwardedto the serial receive input (SR) of a DSP associated with device 41, aswell as the input of detector 54 b. The DSP 60 maintains an input pincapable of accepting non-compliant data, and thus SR can recognize, forexample, SPDIF protocol. If device 50 b is compliant, however, thecompliant information is routed onto BO and, if necessary, is routed tothe DSP via, for example the I²C port. DSP 60 can perform operations onthe data, depending on whether the data is compliant or not. Includedwith those operations is to decode the non-compliant data at SR pin andperform any needed functions by the device. Also, if needed, thenon-compliant data can be re-formatted by operations of the DSP 60 tomake the non-complaint data compliant. Non-compliant data can be sent tothe serial transmit output (ST) port and then to a non-compliantexternal device. If data output from DSP 60 is destined for a compliantdevice, however, the data is presented to controller 56, which operatesto reformat the non-compliant data to an appropriate timeslot andprotocol for compliant data and forwards the data across the network viaBO. Thus, data from DSP 60 can be formatted through a transceiverinterface that includes controller 56. Controller 56 can be integratedtogether with the auto detector and multiplexers as a single interface,as described in FIG. 8.

Placed between BI and RX is controller 56 that operates not only as anetwork transceiver to place BI onto the network, but also to place BIinto device 41 if device 41 is a destination for compliant dataforwarded across the network. Controller 56 takes compliant data andarranges that data into a protocol acceptable to the well known I²C orI²S protocol acceptable to DSP 60. Controller 56, serves as a physicallayer device to synchronize and reformat the incoming data of BI to theDSP-recognizable format. The controller can send reformatted data acrossthe I²C bus to DSP 60. Controller 56 thereby affords compliant networkdata to be placed onto the input of device 41.

Each port thereby includes an interface. Interface 64 of port 44 isillustrated in detail to include multiplexer 58 a, 58 b, detector 54 b,DSP 60 and controller 56. Detector 54 b of FIG. 4 performs autodetection functions. In the example of FIG. 4, detector 54 b comparesthe incoming SPDIF protocol to the network protocol, or compares theincoming Ethernet protocol to the network protocol. A counterpartdetector is not needed on the transmit side of interface 64 sincemultiplexer 58 a either selects compliant or non-compliant datadepending on the status of the external device 50 b connected to the TXoutput of port 64. A configuration register can be programmed tomaintain the compliant/non-compliant status of the external device, andthereby provide the appropriate select signal of C=0 or C=1 to themultiplexer depending on whether the external device is non-compliant orcompliant, respectively. As shown, the configuration register isprogrammed to maintain a selection status of 0 to indicate anon-compliant device is coupled to the TX output of port 44 to ensurethe serial transmit output (ST) of non-compliant data from DSP 60 isforwarded to non-compliant device 50 b. As shown ST can produce SPDIFoutput data recognizable by the RX pin of external device 50 b.

FIG. 5 illustrates two separate detectors: preamble detector/comparator66 and code detector/comparator 68, which can be used to performcomparison functions of detector 54 b. It is recognized that SPDIFprotocol does not utilize time-division, multiplexed channels dedicatedto each frame of information, and the Ethernet protocol contains codingthat is dissimilar from DCA coding or DC-free coding set forth in U.S.Pat. No. 6,437,710.

The 8B/10B code of Ethernet is detected as being dissimilar from DCAcode and, therefore, code comparator 68 will send the comparison resultsto the multiplexer to selectively receive the incoming data or not uponthe receive input of a compliant device within the network. Similar tothe code comparator 68, preamble comparator 66 compares the preambles ofthe SPDIF versus network preambles to determine if there is a protocoldifference. Both code and preamble comparators determine any protocoldifferences to denote whether the incoming data will be sent into theserial input pin which is dedicated to receiving the non-compliant data,or whether the incoming data will be placed on the receive input of theport that is connected to the BO of that port for receiving compliantdata.

FIGS. 6 and 7 illustrate a different type of non-compliant data, whichcan be analog data. A DAC within device 50 b is designed to send leftanalog audio output data and right analog audio output data, with theright analog audio data being sent from the transmit pin of device 50 binto the receive pin of port 44. Receive pin on port 44 is the same pinthat receives the right analog audio data from the DAC. The left analogaudio data is sent from the receive pin of device 50 b to the transmitpin of port 44, as well as the left analog audio input of ADC withininterface 65. As shown, ports 42, 44 and 46 as similar to those in FIG.3; however, within ports 44 is an interface circuit 65 that includes anADC. Interface circuit 67 includes a DAC. Alternatively, instead of theADC and DAC circuit within the interface circuits, the ADC and DAC canbe within distinct regions of the associated device 41 (FIG. 3).

Similar to ADC and DAC circuits within interface circuits 65 and 67 ofports 44 and 46, counterpart DAC 71 and ADC 73 can be placed innon-complaint devices 50 b and 50 c. Importantly, the left and rightanalog audio data of an ADC are placed on the left and right analogaudio pins that are shared with the transmit and receive pins,respectively. Conversely, the left and right analog audio data of a DACare placed on the left and right analog audio pins that are shared withthe receive and transmit pins, respectively. In this fashion, aleft/right audio information can be sent from a DAC to a left/right pins(and transmit/receive pins) of a port associated with an ADC. Left andright information sent by the DAC can be returned by the ADC, and thetransmit/receive right/left convention on the DAC is thereforeconsistent with the receive/transmit right/left convention on the ADC toform a virtual loop network between the ADC and DAC for sending andreceiving analog audio information. As shown in FIG. 6, the ADC can beassociated with a port of a first device or can be within a seconddevice connected to the first device via the port. The same applies tothe DAC.

Also included in FIG. 6 is a detailed view of interface circuits 65 and67, with the ADC and DAC broken out into separate left and right ADCsand DACs. The left analog audio channel is coupled into the left ADC 74.Multiplexer 76 a is coupled to select either serial transmit output (ST)from the DSP or BI from the network. Thus, digital representations of aleft analog audio channel can be selected and sent to the L/TX pin ofport 44 or, alternatively, network data within BI can be sent to theL/TX pin. The analog audio left and right channels can be forwarded fromthe ADCs to the DSP 78, which can be placed in digital form and eithersent onto the network via controller 56 or output via L/TX pin of port44 depending on whether the external device coupled to port 44 iscompliant or non-compliant. The incoming right analog audio channeloperates similar to the left channel in that a right ADC 79 is used toreceive the incoming data and detector 75 determines whether the data iscompliant and, if not, then multiplexer 76 will place BI onto BO. Theanalog data, left and right channels, is forwarded onto DSP 78 and thenonto the internal device associated with port 44 via interface 65.

Similar to interface 65, another interface 67 has similarly situatedcircuit elements and, in particular, left and right DACs broken outseparately from each other. The DACs 74 a and 79 a receive the incomingdata, and form the conversion. A multiplexer 76 a′ is shown and operatessimilar to multiplexer 76 a. The same is said for multiplexer 76 b′ anddetector 75 b′ operating similar to multiplexer 76 b and detector 75 b.A driver circuit can be provided in each interface to drive compliantdata from the network via BI back out to the connected device if theappropriate select signal is provided via the configuration registers.As shown in FIG. 6, the select signal C has been set of 0 to indicateselection of ST output from the DSP to be placed into the non-compliantreceive input of devices 50 b and 50 c. If devices 50 b and 50 c werecompliant, then the select signal C would be set to 1 to indicateselection of BI for placement into their receive inputs.

FIG. 7 illustrates detector 75 b/75 b′ used to compare the frequency ofthe incoming analog signal to the network transfer rate of compliantdata sent across the network between ports. Typically, the digital datasent across the network between BI and BO, and between neighboring BOand BI, is multiples of FSY, where FSY is either 44.1 or 48 kHz. Theanalog signal is typically sent at frequencies less than 30 kHz. The DCbias of the digital signal can be adjusted upward and sent across thenetwork, whereas the DC bias of the analog signal is essentially zero.Adjusting the DC bias forms a distinction if amplitude comparison isdesirable over frequency. Detector 75 a/75 a′ is used to determinewhether the digital signal sent from the DSP is compliant with thenetwork protocol and thus to place it on the network or to forward it tothe non-compliant external device.

FIG. 8 illustrates two interface units 80 and 82 having embedded in themcontroller 56, and the transmit pin of one interface is essentiallyconnected to the receive pin of another interface, as shown, by amultiplexer. Of course, the interface units 80 and 82 can be integratedtogether as one unit if needed. Connection of the transmit and receivepins affords a daisy chain or ring topology to be formed betweeninterface circuits 80 and 82 of ports 100 a and 100 b, respectively. Inaddition, interface 80 and 82 are coupled to form a hub on which adevice (“second device”) can send data. Furthermore, in addition to asecond device 84, and third device 86 can be connected to first device90. The second and third devices shown, in this example, are audio-videoreceivers 84 and 86. The auto non-compliant detection feature enableslegacy consumer equipment, such as CD players, DVD players, and thelike, to be connected into a compliant network, and to transfer acrossthe network at a fixed rate to support a variety of sample rate sourcematerial, such as 44.1 kHz and 48 kHz audio and video information.

The audio-video receiver (compliant or non-compliant) can play audio andvideo information placed into the network from a DVD player 90, or SPDIFinformation sent from DVD player 90 via interface 82. The informationcan be sent over an I²C port or I²S port to the serial receive, SR,input of interface 80 or 82, depending on whether the destinationaudio-video receiver is compliant or not. The controller within theinterface unit will synchronize the incoming data and perform otherphysical layer functions on the incoming data. Audio-video receiver 84and/or 86 can send optical information, for example, into a fiber opticreceiver (FOR) 92 a and 92 b.

To implement auto SPDIF detection, the non-compliant data output fromlegacy device 86 is also connected to the SPDIF serial input, SR, pin ofinterface 82. This pin is configured to receive the SPDIF data. WhenSPDIF is detected, the input multiplexer state is switched to pass theBI from interface 80 onto the RX input of interface 82. Thus, when aSPDIF device 86 is connected, the ring is maintained and, specifically,the communication from one device to the other across the network ismaintained. Information from the network can be transferred back outfrom the network onto the third device 86 via a fiber optic transmitter(FOX) 98 b.

Labeled in dashed line are two ports 100 a and 100 b corresponding tofirst device, e.g., DVD 90. Port 100 a is dedicated to receiving networkinformation as well as compliant data from a compliant device 84. Port100 b, however, is dedicated to receiving both network information andnon-compliant data from device 86. In the example shown, the SPDIF inputis recovered by an asynchronous source port, labeled as the serialreceive (SR) port. Along with the controller, the detector/comparatordescribed above can be integrated into the interface to performs thecomparison, and then a multiplexer is shown to multiplex the appropriatesignal onto the receive pin of the interface. If the SPDIF data is to bereceived, the SPDIF data is transported unlocked isochronously to anasynchronous serial receive port (SR), where the controller within theinterface 82 performs synchronization using a PLL, or other meansdescribed below.

Multiplexers 94 a and 94 b will connect the optical receiver data outsignal to the receive input of interface 80/82 only if light is detectedand SPDIF data is not detected. The status signal of the opticalreceiver is connected to the general purpose input/output of theinterface. If this indicates that light is detected, then the interfacewill monitor the SPDIF lock detector within the corresponding interfaceunit. If lock is not detected within a certain timeframe, then theoptical receiver data out is connected to the receive (RX) input. SPDIFinput may be at 48 kHz or 44.1 kHz, whereas the network may be locked to48 kHz. Software automatically determines the frequency differences andthe comparator determines any preamble differences.

DVD player 90 is typically synchronized to a 27 MHz clock derived from aPLL 104. DVD player 90 provides preferably 96/48 kHz or 88.2/44.1 kHzaudio data. When the DVD rate and the network rate are not equal, theDVD data is transported in locked isochronous mode. Then the DVD andnetwork rates are the same, the DVD data is transported synchronously.The maximum data from the DVD is approximately six channels, 24 bit, and96 kHz. Simultaneously, the DVD provides AC3 encoded data over SPDIF,which is equivalent to CD audio bandwidth. All six channels of 96 kHzaudio plus the AC data can be transported in three isochronous streamssimultaneously. The interface 80/82 will process six channels of 96 kHzaudio and packs those channels into two isochronous channels, while oneDSP on one of the interfaces will pack AC3 into another isochronouschannel.

Transporting data unlocked isochronously typically involves a digitalPLL at the destination device. Thus, PLL 104 (FIG. 8) can be a digitalPLL which formulates the serial clock or sample rate of the destinationdevice from FSY, and the frequency or phase difference between FSY andthe sample clock at the source device. FIG. 9 indicates the unlockedisochronous transport mechanism. Instead of sample rate converting atthe source device, FIG. 9 indicates a digital PLL at the destination114. Source device 105 can be sampled at fs and comparator 106 cancompare the network frame rate FSY to the sample rate of fs=FSY1. Thephase difference ΔΦ1 or the phase difference at time 1 and time 2(ΔΦ1+ΔΦ2) can be sent across the network as a single bit or multi-bitbyte. The phase difference or ΔΦ1 can have a different bit valuedepending on the phase difference magnitude. The sample data can,therefore, be sent as isochronous data at the frame transfer rate ofFSY2, but possibly with an additional byte reserved in each frame toaccommodate a faster FSY1 relative to FSY2. In this fashion, thestreaming data is maintained across each of the successive frames sentacross the network.

Comparator 106 compares the phase difference between the leading orfalling edges of each frame transfer clock or sample clock. A digitalphase comparator 108 can take place using a timer, for example. If threeserial bitstreams are used, for example, a high speed clock can be 3072fs. If, for example, six cycles of 3072 fs separate the trailing edge ofFSY1 and FSY2 (noted as ΔΦ1), then a byte indicating a binary 6 value isperiodically sent across the network. Increasing the clock rate to 24576fs will significantly increase the resolution of the binary value and,therefore, instead of sending 8 bits periodically, 12 bits can be sent.

The phase difference (e.g., an 8-bit byte or 12-bit byte) is thereafterused by the PLL and the destination port. Adder 110 subtracts the phasedifference between FSY1 and FSY2 (represented as A−R), and the phasedifference between FSY2 and FSY1 (represented as B−R) to achieveA−R−(B−R). If those differences are 0 and, thus, the digital PLL 104 islocked, then the output from adder 110 will be 0 phase difference placedinto a filter, divider, and oscillator network 112. Adder 110 andfilter, divider, and oscillator 112 can form a part of a DSP. Phasecomparator 108 compares the network transfer frame rate clock edge tothe local sampling rate of the destination device, shown as reference B.Reference B is made equal to reference A due to the feedback fromdigital filter and programmable divider 112. Divider 112 receives a highfrequency clock from oscillator 112 that, based on the control outputfrom filter 112, divides the oscillator output to the appropriatefrequency and phase needed to lock the local sampling clock B to thesource sampling clock A.

A local digital PLL at the destination device allows any streaming dataat any frequency to be sent unlocked into the network. It is not untilit is received upon destination device 114 will the sampling rate belocked to the sampling rate on the source device 105. Phase and/orfrequency differences can be sent across the network along with theisochronous data as unlocked isochronous data. A digital PLL avoids theuse of complex sample rate conversion mechanism in the source device,and the overhead of a DSP in that device. Instead, a single PLL can beused in the destination port and thereby allow isochronous data to besent across the network with clock recovery being used in thedestination port in lieu of sample rate conversion, or jitter associatedwith localized crystal oscillators.

FIG. 8 illustrates a DVD player 90 sending SPDIF and/ornetwork-compliant data into a network to be received upon a compliant ornon-compliant input of an audio-video receiver. Conversely, FIG. 10illustrates a compliant and non-compliant device sending informationinto the network, or compliant and non-compliant ports of an audio-videoreceiver placed within that network. Specifically, FIG. 10 illustrates acompliant DVD player 120 and a non-compliant CD player 122 sendingincoming data into a network or compliant/non-compliant ports of anaudio-video receiver 124. For sake of brevity, the various details ofeach port 126 a and 126 b are not shown. However, it is understood thatthe fiber optic transmitter and receiver ports, synchronization port,and multiplexers, as well as the functionality of the GPI, SR, and GPOpins of the interface are similar to those shown by ports 100 a and 100b of FIG. 8.

A non-compliant or legacy CD might send left and right audio channeloutputs into the ADC interface. The ADC interface will then forward theaudio information into the DSP of receiver 124 as digital information.Compliant device 120 can also send data into port 126 a. Port 126 a canthen forward the data onto the network, as well as into the DSP ofaudio-video receiver 124 via the serial transmit pin (SX).

Serial clock (SCK) and the frame sync clock (FSY) are derived usingeither the unlocked isochronous transport mechanism of FIG. 9 or alocked isochronous transfer mechanism of FIG. 11. If the source devicecannot be slaved to the network timing, for example a digital videobroadcast receiver, then the FSY and SCK will most likely be derivedfrom the source device using an unlocked isochronous transport mode,where FSY and SCK will be compiled at the destination device from thesource device. However, if the source device does not constitute theclock master and possibly some other device connected to the networkoperates as the master, then the master will essentially be the networkitself. In this fashion, the source device can be slaved from thenetwork master, and the destination device can also be slaved from thenetwork master. In this instance, FIG. 11 illustrates slaving the sourceand destination devices to the network clock master, where the networkframe sync FSY2 is used to compile the source and destination samplerates FSY1=fs.

Referring to FIGS. 10 and 11 in conjunction, PLL 130 at the destinationis shown in FIG. 10. Associated with PLL 130 is a divider and multiplier132. Divider and multiplier 132 will divide and multiply the frequencyby an X/Y factor relative to the network transfer rate of FSY2. Insteadof a separate divider and multiplier, PLL 130 can have a fractionaldivider 132. The fractional divider or separate divider and multiplier132 can actually be made a part of and integrated with multimedia device124.

Referring to FIG. 11, if the network frame sync FSY2 is 48 kHz and thesource and destination sample rate is 44.1 kHz, then a cumulative ratioof 147/160 for the divider multiplier 132 a and 132 b occurs. However,if the network frame rate if 44.1 kHz and the source and destinationsample rate is 48 kHz, then the cumulative ratio is 160/147 withindivider multiplier 132 a and 132 b. As part of a DVD drive, a systemcontroller will control the drive, decode the audio and videoinformation, and convert the audio information to analog, while sendingthe uncompressed video to a display.

The controller is typically clocked by a local 27 MHz crystaloscillator. Alternatively, the crystal can be deactivated and thecontroller can be clocked from a 27 MHz clock that is derived from FSY2.The controller is within interface 134 a and 134 b. As audio data isread from the drive, it is decompressed in the case of a movie and, ifnecessary, is forwarded to a DAC. The sample rate of the DAC is fixedand unchanged, it is generated directly or implicitly from the 27 MHzreference. As an example, a PLL with a frequency conversion ratio of2/1125 will convert the 27 MHz reference clock of the controller to the48 kHz sample clock needed to sample the audio data from the drive. Aconversion ratio of 49/30000 will convert 27 MHz to 44.1 kHz. Thus,source device 136 and destination device 138 can receive data sampled atalmost any frequency, as well as the rate at which the controllerswithin interface 134 a and 134 b operate. Thus, the serial clock and thesample rates can be adjusted based on the divide and multiply factors ofthe local PLLs within both source and destination nodes. A lockedisochronous transport mode can, therefore, be achieved.

Numerous variations and modifications will become apparent to thoseskilled in the art once the above disclosure is fully appreciated. It isintended that the following claims be interpreted to embrace all suchvariations and modifications.

1. A multimedia device, comprising: a series of ports, wherein each port of the series of ports includes a bypass output connected to a bypass input of the next port within the series, and wherein the last port in the series includes a bypass output connected to a bypass input of the first port within the series to form a ring network for communicating between the series of ports; and at least one pin of the multimedia device across which data is transferred between the multimedia device and the ring network.
 2. The multimedia device as recited in claim 1, wherein the data is compliant with or compatible with a format that is similar to a protocol by which network data is transferred across the ring network.
 3. The multimedia device as recited in claim 1, wherein the series of ports comprise: a first port coupled to transfer the data at a first rate from the bypass output pin to the bypass input pin as locked isochronous data; a second port having a phase-locked loop coupled to receive the data and convert the data from the first rate to a second rate slaved to the first rate
 4. The multimedia device as recited in claim 1, wherein the series of ports comprise: a first port coupled to transfer the data at a first rate from the bypass output to the bypass input as unlocked isochronous data, wherein the first port is also coupled to transfer a phase difference between the first rate and a rate in which information is sent from the bypass output to the bypass input; and a second port having an adder coupled to modify the frequency of data is sent from the bypass output to the bypass input depending on a magnitude of the phase difference.
 5. The multimedia device as recited in claim 1, further comprising an interface having a controller arranged between the pin and the bypass output for converting the data from non-compliant data to compliant data before transferring the data from the multimedia device onto the ring network.
 6. The multimedia device as recited in claim 5, wherein the non-compliant data is in a format that is dissimilar to a protocol by which network data is transferred across the ring network.
 7. A communication system, comprising: a first multimedia device having a first port that includes a first port receive input and a first port transmit output; a second multimedia device having a second port that includes a second port receive input and a second port transmit output; wherein the first port receive input and second port transmit output are coupled to transfer digital data and right analog audio data; and wherein the second port receive input and first port transmit output are coupled to transfer digital data and left analog audio data.
 8. The communication system as recited in claim 7, wherein the right analog audio data and left analog audio data are transferred concurrently.
 9. The communication system as recited in claim 7, wherein the first multimedia device includes at least one pin (i) into which right analog audio data and digital data are received, (ii) from which right analog audio data and digital data are transmitted, (iii) into which left analog audio data is received and from which digital data is transmitted, or (iv) from which left analog audio data is transmitted and into which digital data is received.
 10. The communication system as recited in claim 7, wherein the first multimedia device includes at least one pin (i) into which left analog audio data and digital data are received, (ii) from which left analog audio data and digital data are transmitted, (iii) into which right analog audio data is received and from which digital data is transmitted, or (iv) from which right analog audio data is transmitted and into which digital data is received.
 11. The communication system as recited in claim 7, wherein the first multimedia device comprises an analog-to-digital converter, and wherein the second multimedia device comprises a digital-to-analog converter, or vice versa.
 12. The communication system as recited in claim 7, wherein the first multimedia device includes a third port, and wherein the first port further includes a first port input and a first port output, and wherein the third port includes a third port input and a third port output.
 13. The communication system as recited in claim 12, wherein the first port further includes: a comparator that compares a frequency of the digital data with a frequency of the right analog audio data; and a multiplexer coupled to the comparator for transferring the digital data to the first port bypass output if the comparison result indicates a DC bias associated with the digital data and the digital data is in a format similar to a protocol by which data is sent from the first port bypass output to the third port bypass input, otherwise a connection is made between the first port bypass input and the first port bypass output.
 14. The communication system as recited in claim 12, wherein the first port output is coupled to the third port input.
 15. The communication system as recited in claim 14, wherein the first port further includes: a comparator that compares a DC bias upon the digital data with a DC bias upon the left or right analog audio data; and a multiplexer coupled to the comparator for transferring the digital data to the first port output if the comparison result indicates a DC bias associated with the digital data and/or the digital data is in a format similar to a protocol by which data is sent from the first port output to the third port bypass input, otherwise a connection is made between the first port bypass input and the first port output.
 16. The communication system as recited in claim 14, wherein the first port further comprises: an input of a pair of analog-to-digital converters coupled to receive the left and right analog audio data; and a processor coupled to an output of each of the pair of analog-to-digital converters.
 17. The communication system as recited in claim 16, wherein the third port further comprises: another processor for receiving digitally converted said pair of left and right analog audio data; and a pair of digital-to-analog converters coupled to convert the digitally converted said pair of left and right analog audio data.
 18. The communication system as recited in claim 17, wherein the first port further comprises: an interface circuit coupled between the pair of analog-to-digital converters and the first port output for converting the digitally converted said right and left analog audio data to compliant data and forwarding the compliant data to the third port input as synchronous or isochronous data.
 19. The communication system as recited in claim 17, wherein the first port further comprises: a serial input of a processor; and a multiplexer coupled to receive the digital data and to transfer the digital data to the first port bypass output if the digital data is in a format similar to a protocol by which data is transferred between the first port bypass output and the third port bypass input, otherwise the data is sent to the serial input for processing by the processor.
 20. The communication system as recited in claim 19, wherein the protocol comprises synchronous data, packetized data, isochronous data and control data sent in time-division multiplexed time slots within each frame of data sent at the same transfer rate across the network.
 21. The communication system as recited in claim 19, wherein the protocol comprises DC-free encoded data.
 22. The communication system as recited in claim 19, wherein the protocol comprises frames of data transferred at either 48 kHz or 44.1 kHz.
 23. The communication system as recited in claim 19, wherein the serial receive pin is adapted to accommodate Sony/Philips Digital Interface Format (SPDIF) data.
 24. The communication system as recited in claim 19, wherein the serial receive pin is adapted to accommodate a serial bitstream of TCP/IP data. 